How Weight Loss Affects Metabolism
Losing Weight Can Slow Down Your Metabolism.
I believe it is not uncommon to pay a sit-down visit to the bathroom in order to become as light as possible before stepping on the scale. On a related note, many people lost their shit over a recent New York Times article about how significant weight loss crashes metabolism.
It’s an interesting piece that reveals tremendous disparity in resting metabolic rate (RMR) between those who had lost a lot of weight compared against weight-matched controls (people of the same weight who had not lost weight).
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On social media, I saw many who desire to lose weight get discouraged by the piece. And while I’ll never say weight loss is easy, this new research makes it appear hopeless. But it’s far from hopeless, especially once we start actually dissecting the body of research in this area and providing context for the RMR disparity.
First off is the fact the article featured former contestants of the fat-shaming train wreck of a game show called The Biggest Loser. I railed against this abortion of a program in a feature piece for the Guardian last January just before the season premiere and showed that, yes, that kind of extremely rapid weight loss does indeed aggressively dial down resting metabolic rate.
In the NYT piece we learn that even though it’s been years since the show, former contestants Danny Cahill “burns 800 fewer calories a day than would be expected for a man his size,” Dina Mercado burns 437.9 fewer calories per day,” Sean Algaier “burns 458 fewer calories a day,” Amanda Arlauskas “burns 591.1 fewer calories per day,” Rudy Pauls “burns 516 fewer calories a day,” and Tracey Yukich now “burns 211.7 fewer calories per day than would be expected for a woman her size.”
Yikes. It is enough to make anyone think sustainable weight loss is hopeless. Except when put into context. First off is a potential genetic confounding variable.
“The people on The Biggest Loser probably have a strong genetic tendency towards obesity, because the average BMI at the beginning of these contests is at around 50,” said Dr. Karl Nadolsky, an endocrinologist in Bethesda, Maryland. The fact that they were at such a significant body weight in the first place implies a strong possibility that their metabolic rate may have been slow to begin with, which contributed to them becoming obese in the first place. “There is a lot of individual variance with these things,” said Nadolsky.
Now let’s couple this with not just the extreme amount of weight they lost, but the very high rate at which they lost it.
In my piece for the Guardian, former contestant Kai Hibbard told me she was consuming fewer than a thousand calories a day while exercising around eight hours per day. The sheer size of the caloric deficit the show contestants achieve is larger than what is considered “rapid” weight loss in the medical community.
And the biggest thing to take note of is that the contestants were not exactly weight stable during the measurements. I spoke with obesity researcher James Krieger of Seattle, who dissected the study to learn more.
“The best work in this area is by Rudolph Leibel,” Krieger said, referring to a 2008 study published in The American Journal of Clinical Nutrition. Krieger explained the study took people who had lost 10 percent of their body weight or more and ensured they were truly weight-stable by keeping them confined in a metabolic ward and hyper measuring not just caloric intake and expenditure, but carbohydrate and sodium intake (which can affect the body’s water balance). “Their weights were so stable they had less than a 20 gram variance from day to day,” said Krieger.
Why is this important? Because weight fluctuation has an almost immediate effect on RMR. And guess what? The former biggest loser contestants were not weight-stable. On average, they were losing about half a pound a week. Not a lot, but enough to likely affect the results. Krieger also explained that it appears as though these contestants had ramped up their physical activity as well, which would further have a decreasing effect on RMR.
“It’s like when you finally start flossing a week out from the dentist,” said Krieger. He can’t be certain, but logically it makes sense that, knowing this testing was going to take place, and all of these contestants had regained some or even all the weight, they might engage in the weight loss version of last-minute flossing. This hypothesis is supported by the higher-than -expected total daily energy expenditures of the contestants compared to what most research indicates in regards to people who have lost considerable weight.
All these potentially confounding variables put the dramatic differences in RMRs between former TBL contestants and weight-matched controls into better context. Yes, it is true losing weight lowers metabolism. It is also true that if you take two identical twins, and one gains a lot of weight for several years, then loses all that weight to get back down to the same weight as the “never fat” twin, the one who had been fat is going to have a lower RMR than the one who never gained weight, and this imbalance between the twins will likely persist for many years — possibly for life.
And this article doesn’t even get into things such as the way the brain can be rewired to crave highly palatable food, adaptations in hunger hormones, and the difficulty of breaking habits that promote fat gain.
Back to RMR: How big is the imbalance? The answer is: We don’t know for sure. According to the research cited in the TBL article, it seems like the imbalance can be huge. But remember all those confounding variables that contribute to it. Chances are, very few will apply to you in your efforts to lose weight, and the degree of any RMR imbalance you may experience compared to weight-matched controls will likely be of a manageable size.
That is, it you don’t adopt the dumbass The Biggest Loser method of weight loss. The aforementioned study by Leibel, where a metabolic ward was used to ensure participants were weight-stable, saw the persistent lowering of RMR was only about five to eight percent less than weight-matched controls. Those are numbers that can be worked around.
Tortoise Vs. Hare
For my piece in the Guardian I spoke with Eric Ravussin, a professor of human physiology at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, who told me, “On The Biggest Loser the lowering of resting metabolic rate is much more significant than you would expect.”
In 2012, Ravussin helped design a study involving contestants from The Biggest Loser that was published in the Journal of Clinical Endocrinology & Metabolism. “I went to their place (the show’s weight loss ranch) and had a post-doc of mine [go] three more times,” said Ravussin. “We shipped a metabolic cart to measure their metabolic rate and body composition.”
Ravussin and his team compared 12 people from The Biggest Loser and matched them with 12 people who had lost similar amounts of weight via gastric bypass surgery. The surgery group lost a lot more non-fat than the biggest loser group. Both groups lost “fat-free mass” (FFM) — which includes muscle loss — but those who underwent surgery lost 30 percent FFM.
This is easily explained by the fact those on the TV show were exercising like god threatened to shove a lightning bolt somewhere sensitive if they didn’t stay on that treadmill. And even though TBL contestants lost less muscle and more fat through the insane exercise regimen (muscle is more metabolically “active”), their drop in RMR doubled the one of the gastric bypass group.
In other words, despite all the exercise, the metabolisms of the biggest losers crashed hard. Way harder than those who lose weight at a more rational pace. A follow-up study published in 2014 in Obesity found that the disparity in RMR between those who had gastric bypass and TBL contestants persisted.
We’re kind of comparing apples to oranges. Gastric bypass is known to have some RMR-sparing effects that we only partially understand, which is one of the reasons it’s one of the most effective long-term methods of weight loss, with about a 75 percent success rate. In terms of how gastric bypass spares RMR, Dr. Nadolsky went full endocrinology geek on me: “It has to do with very complex neuroendocrine pathology and patho-physiology of obesity from the central neuroendocrine stuff to the peripheral gut hormones and the leptin.” So, uh, yeah. There you go.
But what happens when you compare apples to apples? Slow weight loss via lifestyle change compared to rapid weight loss via extreme measures?
For one thing, people who lose weight fast have a greater loss in fat-free mass (FFM – stuff you don’t want to lose, like muscle) than those who lose weight at a more moderate pace. Dr. Nadolsky explained that he recommends his patients engage in resistance training to prevent such a loss of FFM — mostly for metabolic health, but also because it can make a difference in terms of preventing weight regain.
You’ve likely heard adding muscle amps up RMR, but I pointed out years ago in the LA Times that those numbers are vastly overblown. Nevertheless, preventing the loss of FFM is still a great idea.
There is also the fact that, as both Dr. Nadolsky and James Krieger told me, the size of the caloric deficit does have an effect on RMR during the weight loss stage, but we can’t be certain if a higher rate of weight loss results in a more drastic extended drop in RMR. I mean, we can guess that it might, but the research isn’t there yet to be definitive.
My friend Dr. Yoni Freedhoff, an obesity physician in Ottawa, Canada, recommends a maximum weight loss rate of one pound per 100 pounds of body weight per week. So if you weigh 200 pounds, you can lose at most two pounds per week. But if you’re 300 pounds, you can lose three pounds per week, adjusting this rate downwards as weight is lost. Although he says there are many reasons for not exceeding this rate, such as what has been discussed in this article thus far, his most important reason is that any faster weight loss is unsustainable.
Because, generally speaking, the lifestyle you adopt to lose weight is the one you have to sustain to keep it off. I wrote an article a while back that breaks down the numbers for hitting this maximal recommended rate of fat loss, and even though it’s nowhere near what happens on TV, it still involves pretty aggressive lifestyle change.
Dr. Nadolsky mentioned that research shows people who lose weight faster have a tendency to keep it off. But it’s important to define what “faster” means. A well-known study of 5,145 people published in Obesity in 2011 did a four-year follow up of people who had undergone substantial weight loss. Those who lost weight the fastest were the most likely to keep it off. But it’s important to point out that this “fast” rate of weight loss was still less than a pound a week.
There are a few important things to realize in all of this.
The first is that, because they were not in a metabolic ward, the study of The Biggest Loser contestants was not very well controlled, making it subject to some confounding variables, and is WAY outside what the average person who loses weight will ever experience.
Second is that, while losing weight may make a person have a lower RMR than a weight-matched control who was never fat, it’s probably not going to be that significant of a difference to dramatically increase the challenge of keeping the weight off, especially if you lost the weight at a sustainable pace.
Third is realizing that RMR is only one part of the equation. Total daily energy expenditure (TDEE) is what really matters. How many calories are you burning in a day? If your weight loss journey involves getting more active and you keep your activity level up, you can have a very reasonable TDEE, which allows for eating a rational amount of healthy food and not feeling deprived.
And perhaps the most important factor of all: your attitude. While a lot of TBL contestants regain the weight, some keep it off because of the tremendous pressure of having lost it so publicly. Those who did not lose weight on a game show can also go through a major mental shift that compels them to lose weight.
These stories exist. Losing weight is not easy and requires thoughtful and persistent dedication to steady changes. Yes, there are things your body will do to fight losing weight, but knowledge is power.
And with that knowledge, you can fight back.
Brought it from www.askmen.com